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Ultrasensitive femtosecond two-photon detector with resonantly enhanced nonlinear absorbtion

Höchstempfindlicher Femtosekunden-Zwei-Photonen-Detektor mit resonant überhöhter nichtlinearer Absorption
: Schneider, H.; Maier, T.; Liu, H.C.; Walther, M.; Koidl, P.


Optics Letters 30 (2005), No.3, pp.287-289
ISSN: 0146-9592
Journal Article
Fraunhofer IAF ()
GaAs/AlGaAs; Qwip; autocorrelation; Autokorrelation

We report on two-photon detection based on nonlinear absorption between subbands in quantum wells. Resonantly enhanced nonlinear absorption, 6 orders of magnitude higher than that of typical bulk semiconductors, leads to a threshold power density for quadratic detection as low as 0.1 W/cm2 and to femtosecond time resolution. The approach facilitates dynamic characterization of the optical light field of infrared emitters with unprecedented sensitivity. We also present a new method for determining the intersubband and intrasubband scattering times by means of autocorrelation measurements.